Bimetallic temperature indicator



Oct. 14, 1941. J. 1. LINER BIMETALLIC TEMPERATURE INDICATOR Filed May 20, 1939 Zlb 30 INVENTOR JOSEPH L/NEB Patented Oct. 14, 1941 UNITED STATES PATENT OFFICE BIMETALLIC TEMPERATURE INDICATOR Joseph I. Liner, Toledo, Ohio Application May 20, 1939, Serial No. 274,860

4 Claims. (Cl. 20148) This invention relates to bimetallic heat-responsive devices, more particularly to bimetallic heat-responsive devices adapted to actuate a temperature-indicating means.

The problem of utilizing a bimetallic heat-responsive device to actuate a temperature-indicating means often involves the movement of a temperature-indicating means over a large arc, which is in many instances difiicult to obtain due to the space limitations imposed upon the structure. In the prior art, bimetallic heat-responsive devices in the form of helices and spirals have been proposed to obtain a cumulative deflection so as to provide the necessary arcuate movement of the temperature-indicating means. In other instances, the large arcuate movements of the temperature-indicating means have been obtained by a lever amplification system. These structures gave the required movement within the space limitations but were often inaccurate due to mechanical difficulties and inexpedient to fabricate due to the large number of parts necessary and to the intricacy of their construction.

The present invention contemplates a structure in which a unitary heat-responsive element is used which gives the necessary amplitude of movement within the usual space limitations and yet has a very simple structure, easy to fabricate in mass production and thereby avoid the disadvantages of the structures discussed above. A bimetallic strip is provided in which a series of bends or folds is utilized acting between an anchor and a free end, the deflections under change of temperature being cumulative to give the necessary amplitude of movement of the free end over an are having a relatively large radius. By the use of this structure, the temperature-indicating means can be actuated directly by the free end of the bimetallic strip which obviates the use of all lever systems required in many of the devices shown in the prior art.

The invention further contemplates the provision of a bimetallic element which obtains a large amplitude of movement under change of temperature by the use of a connected series of expansive and contractive bights in a strip of himetallic material, which occupies a minimum of space, and whose deflections are cumulative, so that a temperature-responsive unit may be constructed as compactly as possible without interfering with its operating efficiency.

It is, therefore, an object of this invention to provide a compact construction for a bimetallic heat-responsive device in which the active element is formed with a series of interconnected expansive and contractive bights, the deflections of which under change of temperature are cumulative, so that an end portion of the bimetallic element, adapted to actuate an indicating means, may move over an arc of relatively large radius and of necessary amplitude per unit change of temperature.

It is a further object of this invention to provide a bimetallic heat-responsive device capable of being inclosed in a relatively small space, one portion of which is anchored and the free end is adapted to actuate a temperature-indicating means by swinging an arc of relatively large radius.

It is a further object of this invention to pro vide a heat-indicating device which is actuated directly by a bimetallic element, the free end of which swings over an arc of relatively large radius upon change of temperature, the complete device being mounted in a casing in a minimum space.

It is a further object of this invention to provide a bimetallic element having relatively straight portions connected together in a series of folds by curved portions of relatively small radius, wherein under change of temperature the curved portions will change the angular relation of the relatively straight portions to swing a free end of the element through an arc of relatively large radius.

Other objects and advantages of this invention relating to the arrangement, operation and function of the related elements of the structure, to various details of construction, to combinations of parts and to economies of manufacture, will be apparent to those skilled in the art upon consideration of the following description and appended claims, reference being had to the accompanying drawing forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

Figure l is an elevational view, partly in section, showing the bimetallic strip in retracted position, and including a schematic diagram of connections.

Figure 2 is an elevational view, partly in section, taken along the line 2-2 of Figure 1.

Figure 3 is a plan view taken along the line 3-3 of Figure 1.

Figure 4 is an elevational view similar to Figure 1, showing the bimetallic element in extended position.

Referring particularly to Figure l of the drawing, a metallic casing or body It! is provided having a hexagonal formation [0a suitable for cooperation with a tool such as a wrench or the like, whereby a threaded portion Nib, which is formed on a concentric tubular extension of the casing iii, may be fitted into a shell or body H having a threaded aperture Ha to cooperate therewith. A metallic thimble I2 is provided to cooperate with an internal bore I 3 formed concentrically with the threaded portion IQb to close one end of a chamber [4 which extends into the interior of the casing 10. The thimble I2 is soldered or otherwise suitably attached to the body member so as to form a leak-proof joint l5. The threaded portion iflb and the thimble I2 are in contact with a fluid contained in a passage-way formed between the body II and an inner wall Hb, so that the temperature of the thimble l2 will respond to the temperature of the fluid.

A unitary temperature-responsive assembly [6 is adapted to be mounted upon a cap ll which'is affixed to the body l0 so as to project into the cavity hi formed on the interior of the casing l0 and the thimble l2. Ihe cap I1 is provided with an outwardly extending annular flange E8 to fit inside of an annular flange [9 formed on the easing ii] adjacent the hexagonal portion Illa. A shoulder lilcis' provided on the casing Ii] which is adapted to cooperate with the outwardly extending flange IS on the cap member IT, with a gasket 25 interposed therebetween toform a leakproof joint when the flange I9 on the body member M is rolled over on the outwardly'extending flange Hi to fix the cap permanently in place as is clearly shown in Figures 1, 2 and 4. This construction completely incloses the chamber 54, so

that the conditions therein will be substantially independent of atmospheric changes, so that moisture is prevented from entering into the chamber M to cause corrosion or the like.

On the interior of the cap H, a U'shaped bracket 2i is provided whose base is attached to the interior side of cap ll by mean-s of rivets 22 which also attach binding posts 23 in position on the exterior of the cap. The rivets 22 are carefully insulated from the cap IT by means of insulating plates 25 and by means of insulating washers 25 positioned on the interior of thecap. Apertures I'Ta in the cap, which cooperate with the rivets 2'2, are made considerably larger than the outside diameter of the rivets, so that the rivets may pass through the cap with insulation interposed. The binding posts 3 are adapted for convenient electrical circuit arrangements and are connected to the electrical portions of the device by being providedjwith nibs' 25 in the chamber Hi which cooperate with the heads of the rivets 22. The electrical circuit arrangements will be described hereinafter.

The sides of the U-shaped bracket 2| are provided with slots 25a, adjacent strengthening flanges 2le, in which are positioned the ends of a piece of insulating material Zl, around which is wound a continuous piece of resistance wire 28, the ends of which are soldered to the nibs 26,

placing the resistance 28 in electrical circuit with e the binding posts 23' projecting from the outside of the cap i1. 7

As shown in Figure 1, one arm of the U-shaped bracket 2! is provided with an integral extension 21b which projects a considerable distance into the interior of the thimble [2. A bimetallic strip 33, having heat-dissipating slots 3% in its body, is attached to the extension 'Zib by means of rivet 5| to hold the same rigidly in position and to form an anchor point. aboutwhich the bimetallic strip is adapted to' expand or. contract tion to the temperature.

under change in temperature to move its free end 380 for purposes to be described hereinafter.

The bimetallic strip 30 is provided with bends so as to form a series of bights, two of which are convergent (30a), and the third, 3512, which is positioned between the bights Eta, is formed so as to be divergent at an initial temperature preferably at the low end of the contemplated temperature range. The bimetallic strip is positioned, so that the material having the greatest expansive power is positioned on the interior side of the bight 3 3a and on the exterior side of bight 39b, so that upon an increase in temperature, the bights 30a will tend to open and become divergent, while the bight 3012 will tend to close and become less divergent. This condition of flexure of the bimetallic strip 30 is shown clearly in Figure 4. The flexures of the separate bights tend to be cumulative in their effect upon the free end 350 of the bimetallic strip.

A slide 32 is attached to the free end 38c of the bimetallic strip by means of rivet 33 and is provided with an adjustable contact member 35 which is adapted to slide freely over the surface of the resistance coil 23 so as to make electrical contact with the turns thereof, so that as the temperature changes in the bimetallic strip, the free end 390 will move the contact 34 to various positions on the resistance coil having a propor- At normal temperatures, the free end 300 of the bimetallic strip is conformed to bear against the extension 2 lb with a slight tension to determine the zero position of the device at which the contact member 34 is in its uppermost position on the resistance coil 28 as shown in Figure 1. Upon increase in temperature, the slide 34 is slowly advanced across the resistance coil 28 until it reaches its maximum position as shown in Figure 4 where the free end 300 of the bimetallic strip abuts against a stop projection 2ic formed on the side of the U- shaped bracket 2|.

It is to be understood that upon reversal of the position of the more expansible metal in the bimetallic strip this device can be readily adapted to measure changes in temperature varying below the normal temperature establishing the Zero point without varying from the spirit of the invention.

Referring again to Figure 1, a schematic diagram of connections is illustrated in connection therewith, in which the heat-responsive device described in detail above is used in connection with an indicating instrument described in Serial No. 151,245, filed June 30, 1937. In this type of telemetric indicating instrument, the potentiometer circuit is used, in which the resistance coil 28 is connected across the free ends of the heater coils H, the other ends of the heater coils being connected to a common point leading through a circuit-breaker C to a battery B which has one side grounded. The current flowing through the heater coils H is controlled by the position of the contact 34 on the resistance coil 28 as determined by the temperature of the bimetallic strip 39; the contact 34 being grounded to the casing lil through the bimetallic strip 39' which completes the circuit through the battery and indicating head. As the contact 534 changes its position on the resistance 28, the amount of current flowing through the heater coils H is varied, so that a pointer P, actuated by thermal strips T under the influence of the heater coil H, will assume a position bearing a proportion to the temperature of the bimetallic strip 39.

Should the bimetallic device be used with an indicating instrument, such as described in Patent No. 2,040,060, the circuit is made through the device by using only one of the binding posts 23 inasmuch as the potentiometer circuit is not used in connection with this type of indicating head. It is, therefore, desirable to make contact with only one end of the resistance 28, the circuit being completed to the ground by the contact 34.

It is to be understood that the above detailed description of the present invention is intended to disclose an embodiment thereof to those skilled in the art, but that the invention is not to be construed as limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawing, since the invention is capable of being practiced and carried out in various ways without departing from the spirit of the invention. The language used in the specification relating to the operation and function of the elements of the invention is employed. for purposes of description and not of limitation, and it is not intended to limit the scope of the following claims beyond the requirements of the prior art.

What is claimed is:

1. In a device of the class described, an elongated casing having an open end and provided with exterior attaching means, a cover for the open end of the casing adapted to form a tight seal with the casing, U-shaped bracket means positioned transversely on the cover to carry active elements projecting into the casing, comprising a folded bimetallic element anchored to one arm of the U-shaped bracket to extend substantially to the bottom of the casing and having a free end adapted to sweep the space between the arms of the U-shaped bracket, a resistance element positioned between the arms of the U- shaped bracket and transversely of the casing to cooperate with the free end of the bimetallic strip, so that variations in the temperature of the bimetallic strip will vary the position of the free end thereof in a proportion to the temperature, and binding posts placed in insulated relation on the outside of the cover for convenience in making connection with the active elements to extraneous electric circuits.

2. In a device of the class described, a U-shaped supporting bracket, a resistance unit supported in transverse relation between the arms of the U- shaped bracket, a bimetallic element anchored to one arm of the U-shaped bracket and having its free end adapted to cooperate with the resistance unit by swinging an arc across its surface between the arms of the U-shaped bracket to vary the resistance in an extraneous electric circuit in a proportion to the temperature of the bimetallic element, and stop means on the other arm of the U-shaped strip to limit the maximum movement of the free end of the bimetallic element.

3. In a device of the class described, a threaded body member, a tubular thimble attached to the body member adjacent the threads, a cap cooperating with the body member to form a weather-proof enclosure, supporting means attached transversely to the inner side of the cap having upright members extending normally to the cap, a resistance element extending between the upright members and transversely of the enclosure, a bimetallic strip fixedly attached to one of the upright members and extending to substantially the bottom of the thimble, said strip having a series of at least three folds having bent portions of uniform radii of curvature, one of which is divergent and the others convergent, so that the free end of the bimetallic strip under normal temperature is in substantial touching relation with the fixed end, contact means attached to the free end of the bimetallic strip to slide along the resistance element under the influence of the bimetallic strip when the temperature thereof increases over the normal temperature, stop means to limit the movement of the contact means and binding posts insulatably attached to the cap for convenient connection to an extraneous indicating circuit.

4. In a device of the class described, a supporting member with an aperture, a thimble extending through the aperture to the inner side thereof, said thimble having its open end outwardly of the supporting member, means cooperating with the thimble and the supporting member to hold the thimble in position in the aperture, a cover for the thimble to form an enclosure therewith, a U-shaped supporting bracket attached to the cover on its inner side within the enclosure, a resistance unit supported in transverse relation between the arms of the U-shaped bracket, a bimetallic element anchored to one arm of the U-shaped bracket and having its free end adapted to cooperate with the resistance unit by swinging an arc across its surface between the arms of the U-shaped bracket to vary the resistance in an extraneous electric circuit in a proportion to the temperature of the bimetallic element, and stop means on the other arm of the U-shaped strip to limit the maximum movement of the free end of the bimetallic strip.

JOSEPH I. LINER. 

